Offshore wells are often drilled from a floating vessel, such as a drill ship or a semisubmersible. However, unlike a drilling platform, the floating vessel is in constant motion due to the waves and tides of the ocean. Thus, it is necessary that means be provided to compensate for the motion of the vessel with respect to the ocean floor into which the well is being drilled. An offshore oil well is drilled through a riser pipe extending from the ocean floor to the vessel. A telescoping joint is provided to connect the riser pipe to the diverter and related drilling equipment on board the floating vessel.
The telescoping joint includes a larger outer barrel located at the bottom of the joint and attached to the top of the last riser pipe extending from the ocean floor. A smaller inner barrel is located at the upper end of the telescoping joint and is telescopingly received within the lower and larger outer barrel. The telescoping joint allows the smaller inner barrel to slide up and down within the larger outer barrel and thereby compensates for the movement in the floating vessel which causes changes in the distance between the ocean floor and the vessel due to waves, tides, and other ship movement. A telescoping joint often has an extendable length of over 50 feet.
The larger outer barrel is landed in and supported by a riser swivel tension ring which includes tensioner line shackles having tensioning lines suspended from a compensator on the drawworks. Typically a diverter is mounted on top of the telescoping joint, which in turn is mounted on the riser, BOP stack, wellhead, and downhole casing, through which drilling is performed.
The telescoping joint also has mounted around the outer barrel a plurality of hydraulic lines, circulation lines, and choke and kill lines. Choke and kill lines are high pressure lines typically having an ID of about 3" and often having working pressures of about 15,000 psi. The hydraulic lines are lower pressure lines typically having an ID of about 2" and often have working pressures in the range of 5,000 psi. Circulation lines are lower pressure lines typically of about 4.5" ID and often have working pressures of approximately 5,000 psi. It is necessary to connect each of the hydraulic lines, circulation lines and choke and kill lines to corresponding fluid lines extending to drilling equipment on the floating vessel. To make these connections, female receptacles are mounted on the ends of each of the hydraulic, circulation and choke and kill lines and corresponding gooseneck connectors are mounted on the riser swivel tension ring. According to some prior art techniques, the gooseneck connectors include a block disposed on the riser swivel tension ring having a gooseneck stab which is received by the female receptacles on each of the hydraulic, circulation and choke and kill lines. The gooseneck stabs on the riser swivel tension ring are manually actuated to connect with the female receptacles on the telescoping joint. Such manual connections often require one to two days because of the extreme difficulty in lining up the gooseneck stabs with the female receptacles.
Because of the size and weight of the telescoping joint and the movement of the floating vessel, it is extremely difficult to adjust the seating of the telescoping joint within the riser swivel tension ring and obtain a perfect alignment between the gooseneck stabs, which are fixed in position in blocks on the riser swivel tension ring, and the female receptacles fixed on the telescoping joint. Misalignment occurs due to an angular misalignment and/or radial misalignment between the gooseneck blocks and stabs and the female receptacles. Angular misalignment can occur if the telescoping joint is cocked or tilted in the riser swivel tension ring. In such a case, the telescoping joint is not supported vertically within the riser swivel tension ring, thereby causing the axes of the female receptacles to be at an angle with the gooseneck stabs. Radial misalignment can occur upon the installation of the telescoping joint within the riser swivel tension ring where the tolerances are all stacked in a common direction causing the gooseneck blocks and female receptacles to be out of axial or radial alignment. The tolerances for the alignment of the gooseneck stab and female receptacle are very small such that a radial misalignment of a fraction of an inch or an angular misalignment of a fraction of a degree will prevent the ready connection of the lines. Because the gooseneck blocks are mounted and fixed to the riser swivel tension ring and the female receptacles are mounted and fixed to the telescoping joint, a fixed connection between the gooseneck blocks and female receptacles allows only a very small tolerance to alignment to achieve a successful connection.
In the general area of flexible couplings for pipe, various types of couplings have provided for misalignment. U.S. Pat. No. 4,781,405 teaches a coupling accommodating misalignment in three basic directions, i.e. axial, angular and radial. U.S. Pat. Nos. 4,252,347 and 4,747,622 include a handle on one portion of the coupling for angularly adjusting the connection between two pipes. U.S. Pat. No. 4,436,326 teaches a coupling allowing radial misalignment. U.S. Pat. No. 4,618,173 teaches a swivel coupling for an angular connection. However, these prior art pipe couplings are fixed conduit type swivel connections and are clamped together. None of these couplings are stab connections. Moreover, none of these couplings provides for a floating stab connection which is automatically correcting or self-adjusting in service to accommodate changes in the radial or angular alignment of the joined conduits.